ABSTRACT
AN account was given of the historical development of our ideas in regard to radium. There is an undoubted genetic connection between uranium and radium, for investigation has shown that the amount of radium in minerals is in all cases proportional to their content of uranium. Boltwood found that a preparation of actinium, initially freed from radium, grew radium at a constant and rapid rate. Boltwood at first considered that actinium was this intermediate product and that actinium changed directly into radium. In another case, a solution of actinium was obtained which produced radium faster than the normal. This parent of radium has distinct chemical properties, which allow it to be separated from both actinium and radium. The absence of growth of radium observed in the actinium solution is due to the fact that, by the special method, the parent of radium had been completely separated from the actinium.
